


Date Stay Night

by spasticbirdie



Category: Undertale (Video Game)
Genre: (i mean it's kinda sexual they're both huge dorks about it), Alphyne, Cosplay, F/F, Sexual Roleplay, Trans Female Character, cosplay sex, ladies and gentlemen we're back with the smut, trans undyne
Language: English
Status: Completed
Published: 2017-08-12
Updated: 2017-08-12
Packaged: 2018-12-14 11:00:31
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,848
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11781783
Author URL: https://archiveofourown.org/users/spasticbirdie/pseuds/spasticbirdie
Summary: Undyne prepares a nice and very nerdy surprise for Alphys.





	Date Stay Night

**Author's Note:**

> For @alphyies on twitter, who requested some fluffy Alpynes with a side order of cosplay.

Undyne knew a watched pot didn’t boil, but she didn’t have anything better to do, so she stood in front of the stove and kept a constant eye on the water in the pot, willing it to heat up. _Geez, this is a lot slower than my old stove._

Eventually, she gave up and turned her attention to the rest of the apartment. She’d had a day off, and Alphys hadn’t. It was one in a series of days off that only one of them had, and this time, Undyne had decided to make the most of it.

For one thing, she’d cleaned the apartment. The piles of anime DVDs and videogames were stacked neatly by the TV, the countertops were wiped down and the floors swept, and most importantly, Undyne had moved away the couch to create a big, wide open space right in front of the door.

The space was now occupied by their small dining table, and the table, as well as much of the apartment, was now dotted with candles. She’d drawn the blinds on all the windows; when she hit the lights, it was going to get dark. On the kitchen countertop was a long line of ingredients to cook dinner, much more than the usual pasta or instant ramen.

Undyne was getting ready for the date night to end all date nights.

She turned back to the stove, where the water was finally starting to boil. Dumping in a block of instant ramen, she looked at the recipe on her phone; since they didn’t really have much more in the house than ramen, she’d looked up recipes for _fancy_ ramen. It had taken a little bit of extra shopping, but she’d managed to gather up everything she needed.

Undyne double-checked the instructions. _Boil ramen. Okay. Easy._ She scrolled through the page, looking over the next steps. _Add seasoning add meat okay okay._

The noodles looked like they could handle themselves for a minute, so Undyne went to go check on the bedroom. The floor was free of its usual piles of dirty laundry, magazines, and manga, the bed was made, and more candles sat on the dresser and nightstands. The usual plain sheets had been replaced with thick, soft blankets, a little too warm to sleep under but perfect for lying on top of, and there were about half a dozen extra pillows fluffed and ready at the top of the bed.

 _Man,_ Undyne thought, _this is gonna be romantic as FUCK._

She turned to head back to the kitchen, but before she could leave, she caught sight of the bathroom; just off the bedroom, the door still a little ajar. She swallowed, suddenly feeling a little nervous. _Should probably check on_ that _._

She hadn’t bothered cleaning up the bathroom - it wasn’t exactly a place you’d set a romantic date night - so it was still littered with the detritus of a normal bathroom; toothpaste, makeup, a couple of medication bottles, a hairdryer with a tangled cord, and a mirror with stains of toothpaste.

The one thing that was tidied up was the shower, specifically the shower curtain; slid aside and tucked up in the corner of the bathtub to make space on the shower rod for a single hanger.

Undyne looked at the outfit hanging there, a little nervously.

Then she heard the smoke alarm go off. _Ah, shit._

 

Alphys pulled into her usual parking spot in front of their apartment, turned the car off, and sat back, sighing. It hadn’t been the _longest_ day she’d had recently, but it had been pretty close; between classes, faculty meetings, and general paperwork, she hadn’t had a break all day.

Getting out the car, she looked up to the window of their apartment; the lights were still on. She felt a little jealous of Undyne having the day off.

As she walked to the door and fumbled for her keys, she saw the light in the window suddenly click off. Alphys frowned. _Guess she went to bed? That’s earlier than usual._

 

In the apartment, Undyne poured two bowls of ramen (she thankfully hadn’t lost too much time making a new batch) and admired her work. The ramen looked downright artistic, like something that’d be served in a high-end Asian restaurant. _A long way from burning pasta. And houses._

She flicked the lights off, plunging the apartment into soft, dim candlelight, took a seat in one of the chairs, and waited. _She should be home any minute._

 

The elevator _dinged_ on their floor, and Alphys half-dragged herself to their apartment door. _Well, if she’s already going to bed, guess I’ll just turn in too._

Her keys scraped in the lock.

 

Undyne heard the tumblrs turning and waited expectantly. _Okay okay. Here she comes._

 

Alphys opened the door and stepped into the apartment. “Undyne, I’m home…” Reflexively, her hand swiped the light switch.

“No, d-” Undyne tried to say, but it was too late. The lights came on, turning the romantic lighting into the normal, flat lights of the apartment.

“Don’t wh-” Alphys stopped midway in the same way Undyne had. She looked at the table, sitting in front of the door, the bowls of ramen, and the candles. “Uh… what’s this?”

Undyne, who was half out of her chair from when Alphys hit the lights, settled back down. “Uh. Dinner? Yeah, uh. I made dinner.” Undyne awkwardly settled back down. “It’s. Uh. Like a date night.”

Through her exhaustion, it took Alphys a moment to process Undyne’s words. “Oh. Oh!” She looked around awkwardly, saw her hand was still on the light switch, and flicked it back off. The apartment plunged back into the dim, warm light of the lit candles all around, lighting the apartment almost as well as the normal lights had.

Alphys took a seat, broke the pair of chopsticks, and spooled up some noodles on them.

She took one slurp, and her eyes lit up. “Oh wow, this is-” She didn’t even finish, as she kept slurping a long strand of noodles as Undyne watched, holding back laughter.

Finally, the noodle disappeared into Alphys’ mouth, and she swallowed. “Delicious!”

Undyne grinned, broke her chopsticks, and dug in as well.

* * *

The rest of dinner passed easily, Undyne letting Alphys talk about her day and vent, bringing seconds and thirds of ramen, and just leaning on the table watching her talk, the candlelight playing over Alphys’ face.

Finally, Alphys leaned back, full and satisfied. “Oh wow, that was delicious!”

Undyne grinned. “Glad you liked it!” There was a comfortable silence over the table for a moment as Undyne fidgeted in her chair. Then, all of a sudden, she leaned over the table and blew out the candles lighting it.

Alphys jumped a little in surprise. “Wh- Hey, Undyne…” There was still enough light to see most of the apartment by, but the area around the table had been plunged into darkness.

Alphys heard Undyne’s chair scrape back, and suddenly felt her breath right on her face.

“Meet me in the bedroom,” Undyne whispered.

By the light of the candles, Alphys saw Undyne scurry across the apartment to the bedroom, shutting the door behind her. For a moment, Alphys just sat there in the candlelight, a little surprised, processing what she’d said. Then, like a lightbulb had gone off in her head, Alphys shoved her chair back, nearly knocking it over, and hurried for bedroom as quickly as she could without disturbing the candles.

Inside were more candles, and the bed made up with its extra-soft blankets. Undyne was nowhere to be seen.

“Uh...Unnie?” Alphys whispered. She didn’t really know why she was being so quiet.

“Just a second!” Undyne called from the bathroom. “I’m, uh, getting changed!”

“O-Okay!” Alphys took a seat on the bed, sinking into the blankets. She kicked off her shoes and slid out of her lab coat; she hadn’t even had time to change before digging into dinner. Slipping off her skirt, Alphys pulled her t-shirt over her head; underneath, she was wearing a plain bra and panties, beige.

 _And practically sexless,_ she noted with mixed bitterness and nervousness.

She glanced at the bathroom door, glanced at their dresser, and made up her mind. Shrugging off her bra straps and letting her breasts fall out of the cups, Alphys uncomfortably turned the bra around until she was wearing it backwards; she was awful at unfastening it behind her back. She undid the clasp and shook the bra off, then lifting her legs up, Alphys slid her fingers in the waistband of her panties and pulled them up and off.

With another nervous glance at the bathroom door, Alphys hurried to the dresser and dug through the underwear drawer. Finally, she extracted what she was looking for; Undyne’s Christmas present to her that she still hadn’t found the time or confidence to wear.

 

"I'm getting changed!" Undyne called. 

In the bathroom, she threw off her jeans and t-shirt, which were followed by her sports bra and underwear. The outfit on the hanger waited patiently, and as she stood naked in front of it, she gave it a stinkeye.

_Alright, let’s see if we can get this on in less than a minute._

 

Alphys struggled with her bra again. This one didn’t have clasps and just pulled over her head, but getting it over was a struggle all its own. Finally, the top squeezed over her snout and she got to work fitting her chest into it.

 

 _Okay, so I_ can _get it on in less than a minute,_ Undyne thought as she stared at herself in the mirror.

The challenge now was psyching herself up to go out there. Undyne turned around, still looking at herself in the mirror, lifting her skirt a little. _God how do people even WALK in boots like this._

 

Alphys tugged on her socks, bringing them up to her thighs. They squeezed a little bit, making her reflect bitterly on how this was somehow the biggest size.

The same problem was reflected in the top; it squeezed her chest more than a little, her breasts near to bursting out.

_Hopefully it won't have to stay on for long._

 

Undyne adjusted the snug dress around her chest and tried to deal with the underwear, but gave up almost immediately; panties and her didn't mix on a normal day, and they certainly weren't cooperating now.

_Anyway, they won't be on that long anyway._

 

Finally as satisfied with her clothes as she could be, Alphys straightened up and sat on the edge of the bed, waiting.

 

Undyne put a hand on the bathroom doorknob and took a deep breath.

 

_Ok._

 

_Ok._

 

Calming her nerves, Undyne opened the door and strode into the bedroom with as much confidence and sexiness as she could muster. “Oh, M-”

What she had planned to be the opening bars of the Mew Mew Kissy Cutie theme song died on her lips when she saw Alphys seated on the bed. Her small, scaly girlfriend was wearing a black top that was halfway between a corset and a bra, a shoulderless one-piece that exposed an absolutely scandalous amount of her chest. Her bottom was a skirt so short it hardly went halfway down her thighs, but to compensate, Alphys had a pair of equally black thigh highs, made of some shiny, sleek material. Matching on her arms were a pair of elbow-length gloves, made in the same black latex material. The final details were a black choker around her neck and a black bow on her head.

 _Oh my god,_ Undyne thought, _that's the Valentines present I got her. That one Mew Mew villain cosplay._

 

Alphys sat as sexily as she could on the bed as she heard Undyne open the bathroom door, but her posture was the last thing on her mind when Undyne came out.

Her attempt at an alluring pose turned into a sudden surprised stiffness when she saw Undyne’s outfit. A torso-hugging dress wrapped around Undyne’s upper body, pink and white with frilly shoulder straps, a heart-shaped gem on the chest, and flaring out to a short skirt. Garterbelts of a similar pastel color connected to cream-white thigh highs, and a pair of high-heeled pink boots and a headband with cat ears completed the outfit, her hair tied back to show the ears. The whole ensemble wrapped snugly around Undyne’s fit frame, the short skirt and tight thigh highs especially showing off her toned legs.

 _Oh my god that's the Mew Mew Kissy Cutie: The Movie Special Mew Mew Mega Magic Change dress,_ Alphys thought, her nerdiness taking control for a moment.

 

For a long moment of silence, the two stood in the candlelit bedroom, both thrown by the other's costume change. Undyne was frozen halfway to a Mew Mew pose, Alphys with her legs crossed and her chest rising and falling in the tight corset.

Finally, Alphys broke the silence. Summoning as much haughty, melodramatic villainy into her voice as she could, she let out a high, regal laugh.

“S-so! Finally you've arrived, Princess Mew Mew!”

Undyne blinked, momentarily dumbfounded, then caught on. She snapped into her pose - peace sign horizontally next to her face, feet planted, other hand on the back of her head.

“Give it up, uh, Queen Destructica! Your plans have failed! I, Princess Mew Mew, will be the one to end your dastardly scheme and take you down for good!”

Alphys let out another evil laugh, uncrossing and recrossing her legs. “Why, what could a little girl like you possibly do against me, Queen of Darkness, Mistress of Chaos, Ruler of Evil?”

Undyne struck another pose; hands on her hips, legs straight. “Because all my friends are counting on me!” She began crossing towards the bed, with slow, deliberate steps. “And with the power of my Mew Mew Kiss, I will turn you from your wicked ways!”

Alphys frowned, her villain act slipping. “W-wait, Princess Mew Mew didn't use the Mew Mew Kiss, s-she hit Queen Destructica with the Mew Mew Special Beam…”

Undyne stopped right in front of Alphys, still holding her determined, straight posture. “But that's where you're mistaken, Destructica!”

She leaned slowly forward. Alphys got a glimpse of Undyne’s cleavage, wrapped tightly her dress, her muscular chest and shoulders stretching the dress tight.

“In the manga adaptation of Mew Mew Kissy Cutie The Movie: Battle for Love,” Undyne whispered in a sultry voice, “Princess Mew Mew uses the power of love to change Destructica’s wicked ways.”

Alphys’ breath caught in her throat as Undyne leaned in closer and kissed her, rough lips sliding over Alphys’ smooth ones. It felt like Undyne’s kiss was sapping the strength from her body, and she put up no resistance as her girlfriend climbed onto the bed, slowly getting on top of Alphys until she was sitting in her lap, their lips still locked in a slow, soft, but still very deep kiss.

Undyne wrapped her arms around Alphys, still reveling in the feeling of Alphys’ lips on hers, her girlfriend’s longer tongue sliding comfortably around hers. Unconsciously, she ground her hips forward a bit, a slowly growing hardness between her legs brushing against Alphys’ soft, heavy thighs.

Alphys finally felt Undyne pull away from the kiss, her eyes fluttering as she tried to see through the warm, wonderful haze coming over her mind. She saw Undyne’s face in front of hers, giving her usual sharp-toothed smile.

“And now…” Undyne said mischievously, “Mew Mew Cutie Flash!”

With a single sudden push from Undyne’s strong arms, Alphys was bowled over onto the bed, lying on her back with her legs hanging over the edge. Not a second later, her vision was obscured by a pillow Undyne threw at her, and she felt Undyne’s weight lift off her lap. Alphys sputtered around the soft, over-fluffy pillow in her face and clawed it away. She looked up, and Undyne had vanished.

Before she could question where her Princess Mew Mew had disappeared to, however, she felt Undyne’s smooth, webbed hands resting on her thighs, just above where the latex leggings ended. Undyne’s hands ran up and down her legs for a moment, then settled on her inner thighs and pushing Alphys’ legs apart.

Alphys tried to prop herself up. She caught a glimpse of Undyne looking up at her from between her thighs, felt a sudden coolness as her panties were slid down her legs, and felt a split second Undyne’s hot breath on her groin before the wind was knocked out of her by Undyne’s lips and tongue sliding along the outside of her pussy.

Undyne didn’t have the advantage of Alphys’ long, lizard tongue, and her sharp teeth called for much greater caution, but she made up for it with enthusiasm. Undyne ran her tongue along the outside of Alphys’ wet pussy, up and down in long, slow licks, her fingers moving in and spreading Alphys’ slit open. She sucked once, quickly, on Alphys’ clit, and was rewarded with a gasp from the chubby lizard that knocked her right back over.

Alphys stared at the ceiling, periodically gasping and twitching as Undyne went to work on her. Her legs kicked feebly and her tail swished on the bed next to and underneath her, but Undyne held her steady. Even though she was keeping her teeth well away from Alphys’ sensitive bits, it was like they were making Undyne’s very breath feel sharp and tingly on her snatch.

Undyne heard Alphys moan and shake in her grip; her pussy was now soaked, leaking on the bed beneath her, wet and wanting. Undyne brought her head back and got up, grinning smugly at Alphys. “Ready to admit defeat yet, Destructica?”

Alphys didn’t respond immediately, still reeling on her back. Undyne climbed back up on the bed, moving on all fours until she was looking right down into her chubby girlfriend’s flushed face and lidded eyes and holding her hands, pinning her to the bed.

Slowly, Alphys got her wind back. “N-never…Th-the Queen of Chaos c-cannot be defeated b-by any m-m-mere mortal…”

Undyne grinned again, and pushed her hips forward until she was right up against Alphys. “Give it up, Destructica!” she taunted. “There’s nothing you can do but admit defeat!”

Alphys took a deep breath and looked back up at Undyne. Underneath Undyne’s skirt and through her panties, Alphys could feel her hardening bulge against her hips, Undyne’s hard, muscular thighs rubbing against her thicker, softer ones.

She forced an evil, confident smile. “Ah, b-but that’s where you’re wrong, my dear Princess…” Alphys whispered smugly. “Because I’ve g-got you right where I want you.”

With a sudden effort, Alphys lifted her legs and brought them together around Undyne’s waist. Thinking she was trying to pull her closer, Undyne pulled her hips back and tried to line up with Alphys’ wet snatch, but instead, Alphys rolled to the side, throwing Undyne for a loop and a tumble onto the blankets. Now she was looking up at ceiling, Alphys straddling her hips.

Alphys let out a slightly giddy evil laugh. “Now, Princess Mew Mew, we can discuss your surrender.”

“Never!” Undyne knew she could throw off Alphys easily, but for now she just enjoyed the view; Alphys thick thighs spread apart over her hips, the short skirt doing absolutely nothing to conceal her wet snatch still leaking on Undyne’s crotch. The corset top was doing a little more to hide Alphys’ chest, but that was still only the bare minimum; Undyne could see the darker color of her nipples poking out from the edge, and the yellow skin of her breasts spilled out over the black material, pushed up by the corset. Beneath Alphys’ skirt, Undyne could just see just a few inches of her thighs before they were cut off by the black latex leggings. Best of all, the thighhighs were snug enough (and Alphys’ thighs were thick enough) that they squished the flesh of her legs at the top. Behind Alphys, her tail swished back and forth, slowly but excitedly.

“You don’t appear to be in...a-any state to make such claims,” Alphys said smugly. She could feel Undyne’s erect dick through her girlfriend’s panties, (which she noticed were a pair of limited-edition Mew Mew Kissy Cutie Pawprint Panties) and see a spot of dampness forming on the fabric. Alphys experimentally rubbed her exposed slit against the bulge in Undyne’s panties, and heard the strong girl under her hiss in a short breath in response.

“N-now, we’ll s-see how long you last against m-m-my…” Alphys took a deep breath, doing her best to stay in character. “M-my Endless Black Hole Barrage!”

Alphys’ latex-gloved hands ran down Undyne’s body and disappeared beneath her frilly skirts. Feeling around her girlfriend's waist, Alphys found the twin bows that secured Undyne’s underwear on either side. She had to say, it was _really_ cute underwear; pastel-pink, lacy frills at the edges, and a mischievous-looking cat face on the front.

Alphys was much more concerned with the thickness of Undyne’s dick surging beneath the thin fabric, however. Breath tight with anticipation, Alphys pulled the bows open, letting Undyne’s panties drop free.

Undyne’s dick slipped out into the open, already fully erect. Alphys wrapped gloved hands around it, starting with slow, gentle strokes. Undyne’s dick wasn’t very long, but it was thick enough that Alphys’ thumb and forefinger barely met as they encircled and jerked Undyne off. Along the length of her shaft were a few small slits in her skin, like frills running down it. Her skin felt smooth and damp, half of it the natural dampness of Undyne’s skin and half of it her sweat and precum.

Biting her lip as Alphys stroked her, Undyne resisted the urge to just sit up, throw Alphys off her and onto the bed, and have her way with her. On that other hand, Alphys’ gloved hands sliding up and down her dick felt _really_ good. She sat back, containing her urges, but it got a lot harder when Alphys started grinding her wet pussy against Undyne’s dick while still stroking it.

Alphys felt Undyne’s dick twitching beneath her, heard her big, tough girlfriend suppressing moans, and smiled haughtily. “W-Well, Princess? Are _you_ ready to admit defeat yet?”

“N-never…” Undyne muttered. She didn’t look as tough now, shaking and flushed between Alphys’ thighs. She bucked her hips up a little bit as Alphys rhythmically rubbed against her. “Princess Mew Mew...is the heroine...who never...gives...up…”

The next evil laugh Alphys did was a little forced; she was just as riled up as Undyne was, her juices lubricating Undyne’s dick and making her hands slip up and down the shaft. “W-w-well, then you’ve f-forced my hand.”

Pressing Undyne’s dick down flat against her stomach, Alphys pushed herself forward one last time, letting the full length of Undyne’s dick slide against her. She held in a gasp as Undyne fought back moans of pleasure. Reaching the tip of her dick, Alphys lifted her hips, allowing Undyne’s dick to unstick itself from her stomach and point upwards, tip teasing at Alphys’ wet, open slit.

“N-now, f-face my ultimate attack!”

Even after her confident announcement, Alphys went slow as she dropped down onto Undyne’s dick, taking her an inch at a time until she bottomed out, her shivering pussy tight around Undyne’s dick and Undyne’s balls up against her rear. A wave of pleasure hit her like a truck; after Undyne’s earlier foreplay, she felt more than ready to just cum immediately.

Alphys let out a shaky, satisfied breath, grinding her hips backwards and forwards as she felt Undyne’s thick dick split her open. Underneath her, Undyne had her hands over her mouth trying to suppress her voice, and her eyelids were fluttering. Alphys felt a hint of pride; seeing her normally tough, loud-mouthed girlfriend shaking and shivering like the candle flames lit around them was… _very_ satisfying.

She lifted her hips up, feeling Undyne’s girth pull out just the smallest amount, and had to hold back moans of her own; to put it bluntly, Undyne felt _huge._ Alphys felt the head of Undyne’s dick catch on every little fold inside her, like it was trying to keep her from pulling out. Her legs shook, and Alphys tried her best to keep herself up.

She failed. Legs going out from under her, Alphys dropped back down on Undyne’s dick, bottoming out again and driving all the air from her body. She gasped and moaned and felt herself tighten up again as Undyne’s dick prodded the deepest parts of her pussy.

Beneath her, Undyne barely noticed Alphys shaking on her dick. She was too busy trying not to cum as Alphys’ pussy coiled around her, warm and tight and wet. Undyne felt Alphys’ warmth slowly push off her, exposing her dick once more to air that felt much colder than before, and then gasped as she plunged down again, Alphys’ hips meeting Undyne’s with a wet _slap._

Summoning all the concentration she had, Undyne tried to put on a brave face. “P-P-Princess Mew M-Mew n-never s-surrenders…”

Alphys leaned forward, her torso lying against Undyne’s and her head in the crook of Undyne’s neck. “U-Unnie...I-It’s okay, y-you can, uh…”

“Oh.” Undyne sighed, relieved to finally drop the roleplay. She wrapped her arms around Alphys, hands running up and down her back, feeling the warmth of their bodies together, even through Undyne’s dress and Alphys’ corset.

After a moment’s rest, Undyne’s hand wandered down to Alphys’ rear and gave her butt a squeeze. “Ready to go again?”

Alphys nodded into Undyne’s neck, then slowly lifted herself back up, sighing contentedly as Undyne’s dick shifted inside her. She looked down at her girlfriend, admiring her for a blissful second; the way her dress wrapped so snugly around her torso and threw her abs and breasts into sharp relief, the way the dress left her shoulders mostly exposed, showing off her biceps very well. Moving her hips slightly, Alphys felt Undyne’s toned, smooth thighs under hers, and shivered.

Finally, planting her hands on Undyne’s hips, Alphys slowly started bouncing herself on Undyne’s dick. She went just as slow as before; in and out, letting the slits of Undyne’s dick catch on every little fold of her pussy on their way out. Alphys pulled Undyne’s dick out until just the head remained inside, and then as she pushed back down, sighed with pleasure as she was gently split in two, Undyne filling up the empty space she’d left behind. She moaned and steadied herself by holding onto Undyne’s chest, groping her breasts through the silky material.

With that slow test out of the way, Alphys began to speed up.

Undyne panted as Alphys bounced up and down on her dick, gripping the bedsheets tightly as she watched her chubby girlfriend ride her. Alphys’ pussy was warm, slick, and most of all, so tight around Undyne’s dick that it felt like she was being sucked in. Her thick tail slapped the bed between Undyne’s legs, occasionally slipping and hitting Undyne’s thighs with a sharp sting. The split seconds when Alphys lifted her hips up, taking part of Undyne’s dick out of the warmth of her pussy and into the air that felt like winter in comparison, felt like ages, and when Alphys dropped her hips down again, engulfing Undyne in her warmth again, Undyne felt her dick twitch on the edge of cumming every time.

Alphys got there first, however.

As she sped up, Alphys gripped the frills of Undyne’s dress tightly, squeezing her girlfriend's smaller breasts, her ass slapping against Undyne’s hips with almost enough force to sting, a short, unrestrained gasp bubbling out with each thrust. She felt like there was a waterfall between her legs and Undyne’s dick was the only way to stem the flow. Hunching over her girlfriend as she continued pistoning her hips, Alphys felt the waves of pleasure start to peak.

“Hahh…hah...Nnnnngh, oh god...” was all Alphys managed to pant out before she slammed her hips down one last time, Undyne’s balls against her ass and the tip of her dick against her womb as she came. Alphys suddenly stopped bouncing her hips, only because all the strength had gone out of her legs, and she fell forward again onto Undyne’s muscular torso. Her entire body quivered as she weakly held onto Undyne, moaning blissfully. Alphys’ tail shook and shivered with the rest of her, until it finally settled down, lying limp on the bed.

Feeling Alphys shake like a leaf on top of her, Undyne held her close, arms wrapped around the chubby girl. She kissed Alphys on the head and stroked her back as her orgasms subsided, heavy gasps turning into pleased moans turning into calm, steady breathing.

Finally, Alphys took one last deep, satisfied breath, and turned her face up to return Undyne’s kisses. “U-uh. Thanks. For the sex.”

Undyne snorted mid-kiss. “Uh, you're welcome? I guess?”

Alphys blushed. “Y-you know what I mean!” She delivered a weak punch she didn't really mean to Undyne’s shoulder.

“I know, I know.” Undyne kissed her again. “Glad you liked it, hehe.”

Her strength coming back, Alphys pushed herself up and lifted her hips. With one last little moan, Undyne’s dick, now slick with her cum, popped out into the open air.

As it did, Undyne let out a quiet, wanting, half-suppressed moan. She tried to hide it; she'd meant this to be Alphys’ night, not hers.

Alphys heard her anyway. She looked down, saw Undyne’s dick still fully erect and now wet, slick and shiny, and reddened. “Oh, uh, uh…”

Undyne saw the look on her face and tried to reassure her. “Oh, babe, it's fine, I-”

“O-oh, my god, I'm sorry, I was so, uh, that I didn't notice you-”

“Al, it's fine, you don't have to-”

“I'm s-sorry, I was being so s-s-selfish, I'm-”

“ _No,_ Al, really, it's fine, it's-”

“It's n-not fine!”

Undyne stopped short. Alphys’ chest was heaving as she breathed heavily, this time having nothing to do with arousal. “I-I mean…”

She flailed her hands in the way she did when she had no clue what to say, then threw then up in the way she did when she gave up trying to. Alphys rolled off Undyne and crawled on all fours to the middle of the bed, her tail low.

“I mean, th-the movie ends w-with Princess Mew d-defeating Queen Destructica, r-right?”

Undyne sat up as Alphys lay down on her back, tail tucked to the side behind her. Alphys lifted her legs, and then spread them, hands on her thighs.

She was still blushing, averting her eyes from Undyne. Alphys stared at a candle flickering on the nightstand instead. She kept staring at the candle as she felt the bed creak when Undyne got up.

Alphys flinched as Undyne’s hands rested gently on her inner thighs. “Queen Destructica…”

Alphys blushed again, this time in embarrassment.

“...I give up.”

Alphys kept staring at the flickering flame. “Th-that's not what P-Princess Mew Mew says.”

“Well, in the Mew Mew Kissy Cutie doujin I know you've got in the closet…”

 _Goddamnit,_ Alphys thought.

“...Princess Mew Mew surrenders to Queen Destructica…”

Undyne’s hips pressed against Alphys’, her dick rubbing against her heat, Alphys shivering with the feeling. Her shuddered breath made the flame sputter a little.

“...to lure her in and then…”

Undyne’s hand caressed Alphys’ face, turning it away from the light.

“...steal her heart with a Mew Mew Kiss.”

As Undyne’s lips met Alphys’ with the softest kiss imaginable, she brought her hips back, lined up with Alphys’ slick cunt, and plunged inside, steadily and not-so-slowly. Alphys moaned into Undyne’s mouth, her pussy still sensitive and raw.

Settling her hands back on Alphys’ thighs, Undyne began moving her hips, thrusting into her girlfriend’s pussy steadily and slowly and deep. Alphys’ slit was still a wet, leaking mess, giving Undyne plenty of lubrication. It was an actual challenge to keep from just going faster, the wetness of Alphys’ cunt daring her to speed up-

Alphys reached up and embraced Undyne, her short, heavy arms going around her neck. “Faster…” she managed to whisper before lapsing back into moaning, unresponsive pleasure.

Undyne obliged her. Returning Alphys’ embrace, she squared her hips and began to speed up, her dick making wet, obscene sounds as it thrust in and out of Alphys, their hips slapping together and splashing Undyne’s body with Alphys’ overflowing girlcum.

Alphys moaned lustily, her voice increasing in volume every time Undyne thrust inside. “NnnnNNNNnnnNNN...oh my god, OH my god, UndynnnNNNnnnne, I love you, I LOVE you, I love youuuuuuu…”

Undyne responded by gripping Alphys tightly around the waist, and kneeling on the bed, lifted her girlfriend up and bounced Alphys on her dick. The chubby girl’s moaning voice turned into a gasping one-woman chorus, and Undyne couldn’t keep her voice down either, panting with arousal as Alphys’ pussy squeezed her tight.

Finally, Undyne knew she couldn’t last much longer, as she felt her dick give its last few twitches before hardening to climax. She thrust her hips up one last time, pushing as deep as she could go, dick tickling the entrance of Alphys’ womb and stretching her open. Her balls clenched and she felt the hot stream flowing up through her dick.

With the last of her strength, Undyne smiled at Alphys and threw up a peace sign over one eye. “Mew...Mew...Special...Beam...Cannon!”

Alphys stared at her as she felt Undyne’s warm cum seep into her, then burst out in snorting, giggling laughter as she came as well, so much that she squirted a little onto Undyne’s stomach. Undyne felt Alphys’ pussy wrapping around her shaft, like she was milking her dick.

When she was finally spent, Undyne pulled out of Alphys and rolled off her, lying on the bed next to the chubby girl, both of them spent and satisfied.

Alphys scooched closer to Undyne and kissed her cheek. “Th-that was…”

“Good?” Undyne asked, not without a little pride.

Alphys snorted. “I-I was gonna say ‘dumb and nerdy,’ but yeah. It was good.”

“What!” Undyne cuddled up to her girlfriend. “Whaddya mean, dumb and nerdy?!”

“I m-mean, like,” Alphys let out another snorting giggle. “Mew M-Mew Special Beam Cannon? That's not even one of her attacks.”

“So I improvised! And it's a lot nerdier of you to even _know_ that.”

Alphys laughed again, kissed Undyne again, and rolled away, sitting up. “O-okay, I should p-probably get this off.” She reached down, pulling at the thigh highs.

“Aw, what? Why?” Undyne asked disappointedly.

“W-well…” Alphys blushed and stammered again. “I-I mean, it's a really nice cosplay, a-and it'd be a shame to, uh… ruin it,” she said coyly.

Undyne blinked, a look of comprehension dawning on her face, and she started scrambling to get her own dress off.

The two outfits fell in a pile beside the bed, and stayed there the rest of the night.

**Author's Note:**

> Thanks for reading! Just an fyi, you can find more of my smut, mainly my non-fanfic, original works, here!


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